I remember in the 1970s and 80s milk would go bad after 3 or 4 days. Now it seems to last much longer. Was anything added to milk so that it stays fresh for a longer period of time?
I was just talking to someone about the same thing. My milk will last for close to a month. I buy lactose free milk so thought that might be the reason. I have also wondered if the screw on lid may add to the life somewhat.
There’s no added preservative in your milk.
Some milk is now “ultra pasteurized”, and it can last a month or two without trouble. But even with normal pasteurization, improvements in the supply chain will improve the shelf life in your fridge. Perhaps, in 1970, it took a week to get the milk from the cow to your fridge, and there might have been poor refrigeration at some point. And now, perhaps it only takes four days from cow to fridge, with better refrigeration along the way.
Also, how you handle the milk once you put it in your cart will also affect its spoilage. If the milk is sitting in your cart for twenty minutes, and then a hot car for an hour (while you run another errand) and your fridge isn’t quite as cool as it should be, it will spoil in just a few days. It’ll last much longer if you keep it as cool as possible, maybe with an insulated bag, and you get it in your fridge as fast as possible.
No, nothing added, but pasteurization has gotten better. Most milk now is pasteurized using something called High Temperature Short Time, or HTST, pasteurization. The milk is heated to 161F for 15-20 seconds. This kills 99.999% of the bacteria, yeasts, molds, fungi, etc. that are found in unpasteurized milk. (Yes, to three digits past the decimal point, that’s not a made up number, that’s the requirement.) This makes milk last about 2-3 weeks in the refrigerator, even after it’s opened.
More and more milk now is UHT or “ultra-pasteurized”, meaning it’s been brought to a very high temperature (above 275F) for one or two seconds. This makes the milk shelf stable for 6 months until it’s opened. You generally see these milks in boxy containers over by the soymilk, but some stores stock them with the more conventional milk in the dairy case. Cream is almost always ultra-pasteurized now, and sold in the dairy case. If you take it home, it will last seemingly forever if you don’t open it.
Killing that much bacteria means it lasts longer. Better transportation systems mean you may be getting milk from cow-to-store faster than when you were a kid. Both lead to greater time before spoilage in your fridge.
(Funny side note: excellent pasteurization is a frustration to microbiology teachers. There’s a classic lab experiment in nearly every entry level micro course which involves taking samples of milk and culturing them for bacterial growth to compare “high quality” milk to “low quality milk”. It worked when the lab was first written, but today even “low quality” milk is very nearly sterile before opening. Our lab assistant secretly inoculated half our milk samples with e.coli so some of them would grow something!)
Depends on what kind of milk you’re buying. Some milk is now preserved using a process called UHT. I’ve read about it in regards to organic milk that often needs to be shipped farther and might stay on the shelf longer, but the same might apply to specialty products like lactose-free milk.
Most normal milk is still simply pasteurized. For a while, my wife was buying organic milk from a local dairy. It was pasteurized, non-homogenized, and it would last anywhere from 3 days to 2 weeks. Guessing their quality control just wasn’t up to snuff. We eventually got sick of the high price and inconsistency and switched to a more mass-produced brand that seems to last forever.
Lactose free milk has a longer expiration time than regular milk - it says so right on the carton (well I mean the date is going to be way further ahead than any other milk you see, it’s not something they specifically advertise.)
These days the whole process is much most sanitary than it was in the past. The cows are milked by machine, which then directly transfers the milk into cooling tanks without ever being exposed to air. Everything is designed to get the milk into the mik jug with as little exposure as possible and to the consumer as fast as possible, which means we all have fresher milk for a longer time. The dairy industry has done a great job at this, so great we barely even notice anymore.
This. My uncle owns a dairy, and from the cow to the truck that takes the milk away, the milk is never exposed to anything except completely sterile surfaces, and it’s chilled and kept chilled the entire time. Hooray for modern science!
We get something called ultrafiltered. It lasts longer than regular pasteurized, but has to be refrigerated and doesn’t last as long as UHT milk. It also is not a good starter for making mozzarella cheese; at least some of the casein has been denatured. For that I buy ordinary milk, which has a date of about 3 weeks hence, instead of 5 or 6.
There are also better containers now that block light and are less permeable. The distribution process has also been improved so that the milk gets to the grocery shelves faster. Even with that, I have a preference for very fresh foods, so I won’t use milk after a few days following purchase.
3 weeks? In my experience non-UHT milk has a date of about 10 days from purchase ( just bought some today, freshest in the shop, date is Sep 24). Once it’s opened, four or five days is the limit before it starts to smell slightly off.